Nearly 15 is not a child, but a teenager. One who should have learned by now that families work together and help each other. That's part of the social contract.
Each member of the family should be responsible for some part of the household chores, as well as shared areas. (If you get something out, put it back. If you mess it up, clean it up.)
Doing small errands or helping out with a newborn is not punishment, just a part of family life. She is NOT a "poor girl"- she's being asked to help out just like millions of older siblings all over the world.
This mum isn't expecting her daughter to give up her social life, just to give a hand when she's around. Raising a child to think they don't have to help in a family often leads to selfishness, thoughtlessness, and entitlement. None of those will be useful in life.
What's wrong with raising kids to be kind and helpful? I did; they're good, kind human beings who make a positive difference in the world. I made a lot of mistakes, but helping them become those people is not one of them.